This FIRCA-BB application intends to having a capacity development of a LMIC laboratory (Nguyen Van Trang, co-PI) at the National Institute of Hygiene and Epidemiology (NIHE) in Vietnam on norovirus (NV) research through collaboration with a well established NV research laboratory at the Cincinnati Children's Hospital Medical Center (CCHMC, Jiang, PI) in Cincinnati, Ohio. We will perform field surveillance of NV associated gastroenteritis in Vietnamese children focusing on three currently urgent topics on the virus/host interaction, immunology and evolution of NVs. We will determine the correlation of histo-blood group antigen (HBGA) status with susceptibility to NVs in children hospitalized with acute gastroenteritis; access immune responses to NVs following natural infection of children in clinical and community settings; and study the role of host herd immunity in NV evolution by genetic and antigenic characterization of GII.4 variants in the Vietnamese children. To improve the research capacity of the LMIC laboratory, we will particularly focus on the improvement of the surveillance network, training of laboratory personnel, and transferring or adapting of new technology, including developing new ones based on needs of the LMIC laboratory. Our goal is to have the LMIC laboratory becoming a national reference laboratory and Dr. Trang the national leader in the NV and rotavirus researches in Vietnam. PUBLIC HEALTH RELEVANCE: This FIRCA-BB application will perform field surveillance of noroviruses (NV) associated gastroenteritis in the Vietnamese children focusing on three currently urgent topics on NV research. We will determine the correlation of histo-blood group antigen (HBGA) status with susceptibility to NVs in children hospitalized with acute gastroenteritis; access immune responses to NVs following natural infection of children in clinical and community settings; and study the role of host herd immunity in NV evolution by genetic and antigenic characterization of GII.4 variants in the Vietnamese children. As a further goal we also will focus on the capacity development of our collaborator's laboratory (Nguyen Van Trang, co-PI) in Vietnam on the field surveillance and laboratory diagnosis of NVsand associated illness. Our goal is to have the laboratory become a national reference laboratory and Dr. Trang the national leader in the NV and rotavirus researches in Vietnam.